In an electrophotographic (EP) imaging process used in printers, copiers and the like, a photosensitive member, such as a photoconductive drum or belt, is uniformly charged over an outer surface. An electrostatic latent image is formed by selectively exposing the uniformly charged surface of the photosensitive member. Toner particles are applied to the electrostatic latent image, and thereafter the toner image is transferred to the media intended to receive the final permanent image. The toner image is fixed to the media by the application of heat and pressure in a fuser assembly. A fuser assembly may include a heated roll and a backup roll forming a fuser nip through which the media passes. A fuser assembly may also include a fuser belt and an opposing backup member, such as a backup roll.
In color EP imaging, time to first print from cold start is an important factor. In order to reduce time to first print, fuser assemblies comprising a ceramic heater, an endless fuser belt adapted to move across the ceramic heater and a backup roll have been used. These belt fuser assemblies typically have a low thermal mass resulting in short warm-up times. Example belt fuser assemblies are disclosed in U.S. Pat. No. 6,818,290 B1 and U.S. Patent Application Publication 2006/0067754 A1 (the '754 application), the disclosures of which are incorporated herein by reference. The endless belt disclosed in the '754 application comprises an inner base layer comprising polyimide with a thermally conductive filler, a metal layer adjacent the base layer, a first primer layer adjacent the metal layer, a thermally conductive elastic coating adjacent the first primer layer, a second primer layer adjacent the thermally conductive elastic coating, and an outer release layer.
U.S. Pat. No. 5,411,779 discloses a process for forming a composite tubular article comprising coating a fluoroplastic solution on an inner circumferential surface of a cylinder to form a tubular outer layer made of the fluoroplastic and further coating a poly(amic acid) solution on the inner circumferential surface of the fluoroplastic tubular layer, causing a bullet-shaped or spherical runner to run along the inner circumferential surface on which the poly(amic acid) solution has been coated, and subsequently imidizing the poly(amic acid) to form a tubular inner layer made of polyimide resin.
It is preferred that each layer of an endless belt in a belt fuser assembly have a consistent thickness so as to provide uniform heat transfer from the ceramic heater to substantially the entire surface of a toned substrate passing through the fuser assembly.